System and method for providing ip version interworking for ims access through epc

ABSTRACT

A Packet Data Network Gateway (PGW) network node of an Evolved Packet Core (EPC) for interfacing with an IP Multimedia Core Network Subsystem (IMS) comprises an IP address assignment functionality module configured to assign both IPv4 and IPv6 addresses to a User Equipment (UE) requesting an IPv6 address, a Network Address Translation-Application Layer Gateway (NAT64-ALG) functionality module and PGW configured to translate between IPv4 and IPv6 addresses, a Gx interface toward a Policy Control and Charging Rules Function (PCRF) network node configured to transmit the UE&#39;s IPv4 address to the PCRF, and an SGi interface toward an application node of the IMS configured the UE&#39;s IPv4 address to the application node, and to transmit and receive IP media packets between the IMS and the UE after IPv4 and IPv6 address translation.

FIELD

The present disclosure relates to the field of telecommunications, andin particular this disclosure relates to a system and method for IPv6and IPv4 Mapping in the Packet Data Network (PDN) Gateway (PGW).

BACKGROUND

The Third Generation Partnership Project (3GPP) unites sixtelecommunications standards bodies, known as “Organizational Partners,”and provides their members with a stable environment to produce thehighly successful Reports and Specifications that define 3GPPtechnologies. A mobile device, also called a User Equipment (UE), mayoperate in a wireless communication network that provides high-speeddata and/or voice communications. The wireless communication networksmay implement circuit-switched (CS) and/or packet-switched (PS)communication protocols to provide various services. For example, the UEmay operate in accordance with one or more of an Code Division MultipleAccess (CDMA) networks, Time Division Multiple Access (TDMA) networks,Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA(OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA: includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR) cdma2000 covers IS-2000, IS-95 and IS-856 standards.A TDMA network may implement a radio technology such as Global Systemfor Mobile Communications (GSM). An OFDMA network may implement a radiotechnology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of UniversalMobile Telecommunication System (UMTS). Long-Term Evolution (LTE) is anew release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTEare described in specification documents from an organization named “3rdGeneration Partnership Project” (3GPP). These various radio technologiesand standards are known in the art.

The Evolved Packet Core (EPC) is the latest evolution of the 3GPP corenetwork architecture first introduced in Release 8 of the standard. InEPC, the user data and the signaling data are separated into the userplane and the control plane. The EPC is composed of four basic networkelements: the Serving Gateway (SGW), the Packet Data Network Gateway(PDN GW or PGW), the Mobility Management Entity (MME), and the HomeSubscriber Server (HSS). The EPC is connected to external networks,which can include the IP Multimedia Core Network Subsystem (IMS).

Internet Protocol version 6 (IPv6) is the latest version of the InternetProtocol (IP), the communications protocol that provides anidentification and location system for computers on networks and routestraffic across the Internet. IPv6 was developed by the InternetEngineering Task Force (IETF) to deal with the long-anticipated problemof IPv4 address exhaustion due to a rapid expansion of IP-connectivityin a wide range of consumer devices, appliances, toys, and otherdevices. IPv6 is intended to replace IPv4, which currently still carriesmore than 96% of Internet traffic worldwide. IPv6 uses a 128-bitaddress, allowing 2¹²⁸, or approximately 3.4×10³⁸ addresses, or morethan 7.9×10²⁸ times as many as IPv4, which uses 32-bit addresses andprovides approximately 4.3 billion addresses.

The two protocols are not designed to be interoperable, whichcomplicates the transition to IPv6. Until IPv6 completely replaces IPv4,a mapping or translation between the IPv6 and IPv4 addresses is requiredto enable IPv6-only clients to reach IPv4 networks and services. Thecoexistence of IPv4 and IPv6 is likely to continue for many years tocome.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of an exemplary Evolved PacketSystem (EPS) network architecture according to the present disclosure;

FIG. 2 is a simplified block diagram of network nodes in an EPCincluding a Packet Data Network Gateway (PGW) to provide access to a UEover an untrusted non-3GPP access network;

FIG. 3 is a simplified block diagram and flow diagram of a firstexemplary process performed by the PGW with co-located NAT64functionality configured to provide access to a UE over an untrustednon-3GPP access network according to the present disclosure;

FIG. 4 is a more detailed block and flow diagram of a second exemplaryprocess performed by the PGW with co-located NAT64 functionalityconfigured to provide access to a UE over an untrusted non-3GPP accessnetwork according to the present disclosure;

FIG. 5 is a flowchart of the first exemplary process performed by thePGW with co-located NAT64 functionality configured to provide access toa UE over an untrusted non-3GPP access network according to the presentdisclosure;

FIG. 6 is a simplified flowchart of the second exemplary processperformed by the PGW with co-located NAT64 functionality configured toprovide access to a UE over an untrusted non-3GPP access networkaccording to the present disclosure; and

FIG. 7 is a simplified block diagram of an exemplary embodiment of anetwork node of an Evolved Packet System (EPS) according to the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 is a simplified diagram illustrating an Evolved Packet System(EPS) 10. The EPS 10 may include one or more user equipment (UE) 12accessing the Evolved Packet Core (EPC) 14 over an Evolved UMTSTerrestrial Radio Access Network (E-UTRAN) 16, an access network in LTE(Long Term Evolution) 18. The E-UTRAN 16 includes at least one evolvedNode B (eNodeB) transceiver 20. The eNodeB 20 provides user plane andcontrol plane protocol termination toward the UE 12. The eNodeB 20 maybe connected to other eNodeBs via a backhaul (e.g., an X2 interface; notshown).

The eNodeB 20 are also commonly referred to as a base station, a basetransceiver station, a radio base station, a radio transceiver, atransceiver function, a basic service set (BSS), and an extended serviceset (ESS). The eNodeB 20 provides an access point to the EPC 14 for a UE12. Examples of a UE 12 include a cellular phone, a smart phone, asession initiation protocol (SIP) phone, a laptop, a personal digitalassistant (PDA), a satellite radio, a global positioning system, amultimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, or any other similar functioningdevice. The UE 12 may also be referred to by those skilled in the art asa mobile station, a subscriber station, a mobile unit, a subscriberunit, a wireless unit, a remote unit, a mobile device, a wirelessdevice, a wireless communications device, a remote device, a mobilesubscriber station, an access terminal, a mobile terminal, a wirelessterminal, a remote terminal, a handset, a user agent, a mobile client, aclient, or some other suitable terminology.

The eNodeB 20 is connected by an S1 interface to the EPC 14. The EPC 14includes a Mobility Management Entity (MME) 22, other MMEs, a ServingGateway (SGW) 24, and a Packet Data Network (PDN) Gateway (PGW) 26. TheMME 22 is a node in the control plane that processes the signalingrelated to mobility and security between the UE 12 and the EPC 14.Generally, the MME 22 provides bearer and connection management. Thegateway nodes 24 and 26 are in the user plane, and transport IP datatraffic between the UE 12 and the external networks 28. All user IPpackets are transferred through the SGW 24 and the PGW 26. The SGW 24 isthe connection point between the radio-side and the EPC 14, and routesand forwards user IP data packets while also acting as the mobilityanchor for the user plane during inter-eNodeB handovers, and as theanchor for mobility between LTE and other 3GPP technologies.

The PGW 26 is the connection point between the EPC 14 and the externalpacket data networks 28, and provides IP address allocation as well asother functions for the UE 12. The PGW 26 is the point of exit and entryof data traffic for the UE 12. The PGW 26 is connected to externalnetworks 28 that may include, for example, the Internet, the Intranet,an IP Multimedia Subsystem (IMS) 30, and a PS Streaming Service (PSS). AUE 12 may have simultaneous connectivity with more than one PGW foraccessing multiple Packet Data Networks (PDN). The PGW 26 performsfunctions such as UE IP address allocation, policy enforcement, packetfiltering for each user, charging support, lawful interception, andpacket screening. The EPC 14 further includes the Home Subscriber Server(HSS) 32, which is primarily a database that contains user-related andsubscriber-related information. It also provides support functions inmobility management, call and session setup, user authentication, andaccess authorization.

It should be noted that the radio access network may communicate withthe EPC 14 via one or a combination of gateway nodes, including the PGW,SWG, and a HRPD serving gateway (HSGW).

Although the UE 12 can reach the EPC 14 using E-UTRAN 16, other accesstechnologies are also specified by 3GPP. Existing 3GPP radio accessnetworks are supported. 3GPP specifications define how the interworkingis achieved between an E-UTRAN (LTE and LTE-Advanced), GERAN (radioaccess network of GSM/GPRS) and UTRAN (radio access network ofUMTS-based technologies WCDMA and HSPA). The EPS 10 also allows non-3GPPtechnologies to interconnect the UE 12 and the EPC 14. The term“non-3GPP” means that these access technologies were not specified inthe 3GPP. These include, e.g., WiMAX, cdma2000, WLAN and fixed networks.Non-3GPP access technologies can be further classified as “trusted” and“untrusted” access networks. Trusted non-3GPP accesses can interfacedirectly with the EPC 14. However, untrusted non-3GPP accesses interworkwith the EPC 14 via a network entity called the ePDG (Evolved PacketData Gateway). The main role of the ePDG is to provide securitymechanisms such as IP Security (IPsec) tunneling of connections with theUE 12 over an untrusted non-3GPP network access, such as WLANtechnology.

FIG. 2 is a simplified block diagram of network nodes in an EPC 40including an ePDG 42 to provide access to a UE 12 over an untrustednon-3GPP access network. The ePDG 42 is configured to implement securedata connections between the UE 12 and the EPC 40. The ePDG 42 providesan SWu interface 44 and acts as a termination node of IPSec (encrypted)tunnels at the SWu interface 44 established with the UE 12. The IPSectunnels are used to perform secure transfer of authenticationinformation and subscriber data over the untrusted interfaces andbackhauls. The IPSec protocol suite uses cryptographic security servicesto protect communications over IP networks. The IPSec protocol suitesupports network-level peer authentication, data origin authentication,data integrity, data confidentiality (encryption), and replayprotection. The ePDG 42 is configured to implement the S2b interface 46with either GPRS Tunneling Protocol (GTP) or Proxy Mobile IPv6 (PMIPv6)for the control plane and user plane, respectively, toward the PGW 50.

Instead of or in addition to the ePDG 42, the PGW 50 can be coupled toan SGW 43 over an S5/S8 interface 47, and/or an Serving GPRS SupportNode (SGSN) 45 over a Gn/Gp interface 49. The SGW 43 is coupled to aRadio Access Network (RAN) 51 via an S1-u interface 53. The SGSN 45 iscoupled to the RAN 51 via an Iu-PS interface 55. The RAN 51 is coupledto the UE 12 via the air interface Uu 57.

The GPRS Tunneling Protocol (GTP) is a group of IP-based communicationprotocols used to carry General Packet Radio Service within GSM, UMTSand LTE networks. In 3GPP architectures, GTP and Proxy Mobile IPv6-based(PMIPv6) interfaces are specified on various interface points. GTP canbe decomposed into separate control and user plane protocols, GTP-C andGTP-U. GTP-C is used within the packet core network for signalingbetween gateways to activate a session on a user's behalf (e.g., PDPcontext activation), to deactivate the same session, to adjust qualityof service parameters, or to update a session for a subscriber who hasjust arrived from another Serving GPRS Support Node (SGSN). GTP-U isused for carrying user data within the packet core network and betweenthe radio access network and the core network. The user data transportedcan be packets in any of IPv4, IPv6, or PPP formats. The GTP-U protocolis used over S1-U, X2, S4, S5, S8, S12, and S2b interfaces of the EPS.For some of the GTP-based interfaces (e.g., S5, S8, or S2b) between thegateways in the EPS network, an alternative option is to use PMIPv6. Theuser plane for PMIPv6-based interface uses the GRE encapsulation fortransporting user data.

The PGW 50 may include one or more data transfer devices (or networkdevices), such as a gateway, a router, a switch, a firewall, a networkinterface controller, a hub, a bridge, a proxy server, an opticaladd-drop multiplexer, or some other type of device that processes and/ortransfers data. The PGW 50 may provide connectivity of the UE toexternal PDNs by being a traffic exit/entry point for the UE. The UE maysimultaneously connect to more than one PGW for accessing multiple PDNs.The PGW 50 may also act as an anchor for mobility between 3GPP andnon-3GPP technologies.

The PGW 50 includes a Policy and Charging Enforcement Function (PCEF)that encompasses policy enforcement and flow-based chargingfunctionalities. The PGW 50 provides control over the user plane traffichandling and its QoS, and provides service data flow detection andcounting as well as online and offline charging interactions. For aservice data flow that is under policy control, the PCEF allows theservice data flow to pass through the PGW if the corresponding gate isopen. For a service data flow that is under charging control, the PCEFallows the service data flow to pass through the PGW if there is acorresponding active Policy and Charging Control (PCC) rule and, foronline charging, the online charging system has authorized theapplicable credit with that Charging Key (Rule Base). The PCEF may let aservice data flow pass through the PGW during the course of the creditre-authorization procedure.

The PGW 50 is coupled to a Policy Charging and Rule Function (PCRF) 52via a Gx interface 54. The PCRF is the central entity that makes policyand charging decisions based on input from different sources, includingmobile operator configuration, user subscription information, servicesinformation, etc. The policy and charging decisions are thencommunicated to the Policy and Charging Enforcement Function (PCEF) orPGW in the form of PCC rules, which contain Service Data Flow (SDF)information that allows identification of IP traffic, chargingparameters that are used to charge this traffic, and quality-of-service(QoS) parameters to be applied to the IP traffic that the SDF filtersidentify. The Gx reference point is used for provisioning of PCC rulesfrom the PCRF 52 to the PGW 50 and the transmission of traffic planeevents from the PGW 50 to the PCRF 52. A PCC rule may include the rulename, a service identifier, service data flow (SDF) filters, gatestatus, Quality of Service (QoS) parameters, charging key, monitoringkey, and other parameters. The PGW 50 also has an SGi interface 56 to aPacket Data Network (PDN) including an interface node called anApplication Function (AF) 58 that does not support IPv6 in this example.In some networks, the AF is embodied as a Session Border Controller(SBC). The AF 58 offers applications that require the control of EPSbearer resources, and communicates with the PCRF 52 to transfer dynamicservice information. An Rx reference point 60 is located between thePCRF 52 and the AF interface 58 in the IMS 62. The Rx interface 60 isused to exchange application level session information between the PCRF52 and AF 58.

As shown in FIG. 2, the UE 12 is an IPv6-only clients, mobile handset,or mobile station. It is only capable of activating IPv6 Packet DataProtocol (PDP) contexts. IPv6 networks are deployed both by migratingexisting IPv4 networks to IPv6 and by building native IPv6 networks.Network planners need to include mechanisms for local coexistencebetween IPv6 and IPv4 infrastructures, in addition to the continuedinterworking of both protocols with the rest of the Internet—includingnew IPv6-only networks. Therefore, a mis-match in the address space ofthe UE 12 and IMS 62 exists and must be addressed. NAT64 Domain NameSystem (DNS) 64 is one mechanism that allows IPv6-only clients tocommunicate with IPv4-only hosts using address and protocol translation.Existing solutions require modifications to be made in the PCRF and/orAF in order to implement mapping between the two protocols. The presentdisclosure describes a system and method of performing such translationor mapping within the PGW functionality without modifying the PCRF orAF.

FIG. 3 is a more detailed block and message flow diagram of an exemplaryembodiment of a system and method for IPv6 and IPv4 Mapping in the PGWaccording to the present disclosure. As shown in FIG. 2, the IPv6 UE 12is coupled to the ePDG 42 via the SWu interface 44 using the IPSecprotocol to establish secure data transmission. The ePDG 42 is coupledto the PGW 50 via a S2b interface 46 transporting user plane data via,for example, a GTP-U tunnel. The PGW 50 encompasses the NAT64 DomainName System (DNS) 64 Application-Level Gateway (ALG) translationfunctionality 70 with access to a Network Address and Port Translation(NAPT) table or database 72. The PGW 50 establishes Gx sessions with thePCRF 52 to provision policy charging and control rules, and the AFestablishes Rx sessions with the PCRF 52 to exchange application levelsession information.

Referring to the message flows illustrated in FIG. 3, the IPv6 UE 12initiates the Attach procedure by the transmission, to the eNodeB, of anAttach Request. The UE network capabilities indicate the supported NASand AS security algorithms, and the PDN type indicates the requested IPversion (IPv6). The Protocol Configuration Options (PCO) message 80 isused to transfer parameters including the IP version between the UE 12and the PGW 50. The PCO 80 may include an indication that the UE 12prefers to obtain an IPv6 address. At the PGW 50, both IPv4 and IPv6addresses are allocated to the UE 12, step 82. The PGW supports dynamicIP address assignment to subscriber IP PDN contexts using the DynamicHost Control Protocol (DHCP). The PGW includes local IPv4/IPPv6 addresspools for assigning IP addresses to UEs on a per-PDN basis. The PGW 50then initiates a Gx session with the PCRF 52 to request and provisionPCC rules. A Credit Control Request (CCR) message 84 is sent by the PGW50 to the PCRF 52 that includes the allocated IPv4 address for the UE 12or UEv4. Other message parameters may include the International MobileSubscriber Identity (IMSI) and Mobile Subscriber ISDN Number (MSISDN) ofthe UE 12. The PCRF 52 in response replies with a Credit Control Answer(CCA) message 86 that includes PCC rules.

The PCC rules may contain Service Data Flow (SDF) information thatallows identification of IP traffic, charging parameters that are usedto charge this traffic, and quality-of-service (QoS) parameters to beapplied to the IP traffic that the SDF filters identify. SDF filters(flow identifiers) are configured in the PCC rules to classify IPpackets to a Service Data Flow. SDF filters in the PCC rules enforcetransport of uplink and downlink IP flows in the appropriate EPS bearer.If an IP packet matches the SDF filter, and the gate of thecorresponding rule is open, the packet is forwarded to its destination.In this example shown in FIG. 3, the PCRF 52 did not provide any filtersto the PGW 50. The PGW 50 proceeds to reply to the UE with the UEv6address allocated to it (88).

The UE 12 sends an SIP Register message 90 that includes the IPv6address allocated to it. The NAT64 ALG (Application Layer Gateway)functionality 70 in the PGW 50 performs translation of the UE's IPv6address to the IPv4 address 92, and an SIP Register message 94, now withthe IPv4 address, is passed on to the AF 58. The AF 58 initiates an Rxsession with the PCRF 52 by sending a Diameter AuthenticationAuthorization Request (AAR) message 96 with the UE's IPv4 address to thePCRF 52 over the Rx interface. The AAR message 96 may include the IMSIand Mobile Station International Subscriber Directory Number (MSISDN) ofthe UE 12. The PCRF responds with a Diameter AuthenticationAuthorization Answer (AAA) message 98. Upon receiving the AAA message98, the AF 58 replies to the PGW 50 with a 200 OK message 100. The PGW50 in turn responds to the UE with a 200 OK message 102.

FIG. 4 is another simplified block and message flow diagram showing anexemplary process according to the present disclosure. An SessionInitiation Protocol (SIP) invite message that includes SessionDescription Protocol (SDP) offer information, INVITE (SDP_(AFv4)) 200,which includes the SDP answer information containing the IPv4 address ofthe AF, is sent from the AF 58 to the PGW 50 over the SGi interface. SIPis an application-layer protocol for establishing, terminating, andmodifying multimedia sessions. SDP is a protocol that is intended to beused to describe a multimedia communication session for the purposes ofsession announcement, session invitation, and parameter negotiation. TheSDP invite message 200 is received by the PGW 50 and is translated byits NAT64 functionality 70 to an SDP invite message that includes anIPv6 address, INVITE (SDP_(ALGv6)) 202, which includes the SDP answerinformation that contains the IPv6 address of the ALG, and transmittedto the UE 12 via the ePDG 42 and a default EPS bearer 204 assigned tothe UE 12 that is attached to the network. The default bearer representsa set of network parameters that define how the data will be treated interms of bit rate, QoS, etc. The default bearer has an associated IPaddress. The UE 12 responds by sending an SIP 18x provisional responsemessage, 18x (SDP_(UEv6)) 206, which includes the SDP answer informationcontaining the IPv6 address allocated to the UE, to the PGW 50. The PGW50 again translates the IPv6 address to the IPv4 address and transmitsthe 18x message, 18x (SDP_(UEv4)) 208, which includes the SDP answerinformation containing the IPv4 address allocated to the UE, to the AF58 over the SGi interface.

In response to the 18x message 208, the AF 58 initiates an Rx sessionwith the PCRF 52 by sending an AA Request (AAR) message (SDP_(AFv4),SDP_(UEv4)) 210 that includes the SDP information containing the IPv4address of the AF and allocated to the UE. The AAR message 210 includesthe characteristics of the media negotiated in the SDP information. TheAAR message 210 may include session, media, and subscriber relatedinformation. In response to receiving the AAR message 210 at the Rxinterface, the PCRF 52 sends a Re-Authenticate Request (RAR) message 212that includes the Service Data Flow (SDF) or IP filters based on theIPv4 address received from the AF to the PGW 50 via the Gx interface.The RAR message 212 may include the rule name, filters, gate status, QoSparameters, charging keys, monitoring keys, etc. The PGW 50 executes thePCC rules and translates the received IP filters from IPv4 to IPv6, instep 214. In step 216, the PGW 50 proceeds to set up a dedicated EPSbearer 218 with the ePDG 42. The dedicated bearer provides a dedicatedtunnel with a guaranteed bit rate for the UE's media packet traffic thatis in addition to the default bearer 204, while the default bearer isused for signaling messages related to the IMS network. The PGW 50 alsoreturns a Re-Authentication Answer (RAA) message 220 to the PCRF 52. TheRAA message 220 may include IP CAN bearer attributes, request type, andsubscriber related information. The PCRF 52 then sends an AuthenticationAuthorization Answer (AAA) message 222 to the AF 58.

The AF 58 may now forward media packets to the PGW 50 (224) using theIPv4 address and the dedicated bearer 218. The NAT64 ALG function 70 ofthe PGW 50 performs translation between IPv4 and IPv6, including the IPversion interworking within SIP messages, in step 226, and thetranslated filters are applied to process the media packets 228translated to IPv6, in step 230. If PCC is enabled, the PCEF in the PGW50 selects the applicable PCC rule for each received uplink IP packetwithin an IP CAN bearer by evaluating the packet against the SDF filtersspecified in the PCC rules. The media packets are then transmitted tothe ePDG 42 on the dedicated bearer 218 according to the SDF filters, instep 232. The media packets are further transmitted over the IPSectunnel 234 to the UE 12.

FIG. 5 is a flowchart of the first exemplary process 300 performed bythe PGW with co-located NAT64 functionality configured to provide accessto a UE over an untrusted non-3GPP access network according to thepresent disclosure. In block 302, the PGW 50 receives a ProtocolConfiguration Options (PCO) message from the UE that includes anindication that the UE prefers to obtain an IPv6 address. At the PGW 50,both IPv4 and IPv6 addresses are allocated to the UE, in block 304. ThePGW includes local IPv4/IPPv6 address pools for assigning IP addressesto UEs on a per-PDN basis. The PGW 50 then initiates a Gx session withthe PCRF 52 to request and provision PCC rules. In block 306, a CreditControl Request (CCR) message is sent by the PGW 50 to the PCRF 52 thatincludes the allocated IPv4 address for the UE 12 or UEv4. Other CCRmessage parameters may include the International Mobile SubscriberIdentity (IMSI) and Mobile Subscriber ISDN Number (MSISDN) of the UE.The PCRF 52 in response replies with a Credit Control Answer (CCA)message. The PGW 50 proceeds to reply to the UE with the IPv6 or UEv6address allocated to it, in block 308.

The PGW receives, from the UE, an SIP Register message that includes theIPv6 address allocated to it, in block 310. In block 312, the NAT64 ALG(Application Layer Gateway) functionality in the PGW 50 performstranslation of the UE's IPv6 address to the IPv4 address, and an SIPRegister message 94, now with the IPv4 address, is passed on to the AF.In response, the AF initiates an Rx session with the PCRF 52 by sendinga Diameter Authentication Authorization Request (AAR) message with theUE's IPv4 address to the PCRF 52 over the Rx interface. The AAR messagemay include the IMSI and MSISDN of the UE. The PCRF responds with aDiameter Authentication Authorization Answer (AAA) message. This resultsin the ability for the PGW to transmit media packets between the UE andthe IMS and perform address translation therebetween.

FIG. 6 is a simplified flowchart of the second exemplary process 320performed by the PGW with co-located NAT64 functionality configured toprovide access to a UE over an untrusted non-3GPP access networkaccording to the present disclosure. In block 322, the PGW receives anSession Initiation Protocol (SIP) invite message that includes SessionDescription Protocol (SDP) offer information, INVITE (SDP_(AFv4)), fromthe AF over the SGi interface. The Invite message includes an IPv4address of the AF. In block 324, the SDP invite message is received bythe PGW 50 and is translated by its NAT64 functionality module to an SDPinvite message that includes the IPv6 address of the ALG, INVITE(SDP_(ALGv6)), and transmitted to the UE via a default EPS bearerassigned to the UE. In block 326, the PGW receives an SIP 18xprovisional response message, 18x (SDP_(UEv6)), from the UE thatincludes the SDP answer information containing the IPv6 addressallocated to the UE. In block 328, the PGW 50 again translates the IPv6address to the IPv4 address and transmits the 18x message, 18x(SDP_(UEv4)), the SDP message that contains the IPv4 address allocatedto the UE, to the AF over the SGi interface.

In response to the 18x message 208, the AF 58 initiates an Rx sessionwith the PCRF 52 by sending an AA Request (AAR) message (SDP_(AFv4),SDP_(UEv4)) that includes the SDP containing the IPv4 address of the AFand the IPv4 address allocated to the UE. The AAR message includes thecharacteristics of the media negotiated in the SDP information. The AARmessage may include session, media, and subscriber related information.In response to receiving the AAR message at the Rx interface, the PCRF52 sends a Re-Authenticate Request (RAR) message that includes theService Data Flow (SDF) or IP filter rules to the PGW 50 via the Gxinterface, in block 330. The RAR message may include the rule name,filters, gate status, QoS parameters, charging keys, monitoring keys,etc. The PGW 50 executes the PCC rules and translates the received IPfilters from IPv4 to IPv6, in block 332. In block 334, the PGW 50proceeds to set up a dedicated EPS bearer with the ePDG. The dedicatedbearer provides a dedicated tunnel with a guaranteed bit rate for theUE's media packet traffic that is in addition to the default bearer,while the default bearer is used for signaling messages related to theIMS network. The PGW 50 also returns a Re-Authentication Answer (RAA)message to the PCRF 52. The RAA message may include IP CAN bearerattributes, request type, and subscriber related information. The PCRF52 then sends an Authentication Authorization Answer (AAA) message tothe AF.

In block 336, the AF may now forward media packets to the PGW 50 usingthe IPv4 address and the dedicated bearer. The NAT64 ALG functionalitymodule of the PGW 50 performs translation between IPv4 and IPv6, and thetranslated filters are applied to process the media packets translatedto IPv6. In particular, the IP version translation is limited to the IPheader and replacing IPv4 with IPv6 addresses with the SIP message. Thetranslation of IP filters is done by the PGW with help from the NAT64ALG function. If PCC is enabled, the PCEF in the PGW 50 selects theapplicable PCC rule for each received uplink IP packet within an IP CANbearer by evaluating the packet against the SDF filters specified in thePCC rules. The media packets are then transmitted to the ePDG on thededicated bearer according to the SDF filters. The media packets arefurther transmitted over the IPSec tunnel to the UE.

By incorporating the IPv4 and IPv6 mapping or translation process in thePGW, no other network node or functionality need to be modified toaccommodate an IPv6 UE accessing IPv6 resources or networks acrossexisting IPv4 infrastructure. The PGW assigns both IPv4 and IPv6addresses to the UE, but interfaces with the PCRF and the AF using onlythe UE's IPv4 address. The PGW takes care of address and filtertranslation so that the AF, IMS, and PCRF are not aware that it isdealing with a UE with an IPv6 address.

In this disclosure, the term “module,” “node,” and “function” may beused to refer a physical circuit or collection of hardware components, aprocessor-based system, a logical code module, functionality, and/or acombination of hardware and software entities. The processes describedherein may be generally implemented by executing specialized softwarecode on one or more microprocessors with the attendant memory,input/output ports, busses, logic circuits, and other peripheralhardware circuits and devices.

It should be noted the present disclosure contemplates that in someimplementations the ePDG and the PGW may be co-located or integratedwith one another in the same “box,” chassis, or node. However, the PGWfunctionality is still the primary logic or module responsible for theIPv4 and IPv6 mapping or translation process described herein.

FIG. 7 is a simplified block diagram of an exemplary embodiment of anetwork node of the Evolved Packet System (EPS) 10. As illustrated,network node 350 may include a bus 352 interconnecting a processor 354,a memory 356, a communication interface 358, an input device 360, and anoutput device 362. The bus 352 enables communication among thecomponents of network node 350. The processor 354 may include one ormore processing units or microprocessors that interpret and executecoded instructions. In other implementations, the processor 354 may beimplemented by or include one or more application-specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), or the like.

The memory 356 may include a random access memory (RAM) or another typeof dynamic storage device that stores information and instructions forexecution by the processor 354. The memory 356 may also include aread-only memory (ROM) or another type of static storage device thatstores static information and instructions for the processor 354. Thememory 356 may further include other types of magnetic or opticalrecording medium and its corresponding drive for storing informationand/or instructions.

The communication interface 358 may include any transceiver-like deviceand antenna that enables the network node 350 to communicate via radiofrequency with other devices and/or systems. The communication interface358 may further include interfaces, ports, or connectors to otherdevices.

The input 360 may include one or more devices that permit an operator toenter information to the network node 350, such as a keyboard, a keypad,a mouse, a pen, a touch-sensitive pad or screen, a microphone, one ormore biometric mechanisms, and the like. The output 362 may include oneor more devices that outputs information to the operator, such as adisplay, a printer port, a speaker, etc.

As described herein, the network node 350 such as the PGW 50 may performcertain operations in response to the processor 354 executing softwareinstructions contained in a computer-readable medium, such as memory356. A computer-readable medium may be defined as a physical or logicalmemory device. A logical memory device may include memory space within asingle physical memory device or spread across multiple physical memorydevices. The software instructions may be read into memory 356 fromanother computer-readable medium or from another device via acommunication interface 358. The software instructions contained in thememory 356 may cause processor 354 to perform processes describedherein. Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, implementations described herein are not limited to anyspecific combination of hardware circuitry and software.

The features of the present invention which are believed to be novel areset forth below with particularity in the appended claims. However,modifications, variations, and changes to the exemplary embodimentsdescribed above will be apparent to those skilled in the art, and thesystem and method described herein thus encompasses such modifications,variations, and changes and are not limited to the specific embodimentsdescribed herein.

What is claimed is:
 1. A Packet Data Network Gateway (PGW) network nodeof an Evolved Packet Core (EPC) for interfacing with an IP MultimediaCore Network Subsystem (IMS), comprising: an IP address assignmentfunctionality module configured to assign both IPv4 and IPv6 addressesto a User Equipment (UE) requesting an IPv6 address; a Network AddressTranslation-Application Layer Gateway (NAT64-ALG) functionality moduleconfigured to translate between IPv4 and IPv6 addresses; a Gx interfacetoward a Policy Control and Charging Rules Function (PCRF) network nodeconfigured to transmit the UE's IPv4 address to the PCRF; and an SGiinterface toward an application node of the IMS configured the UE's IPv4address to the application node, and to transmit and receive IP mediapackets between the IMS and the UE after IPv4 and IPv6 addresstranslation.
 2. The PGW network node of claim 1, wherein the Gxinterface is further configured to provision Policy and Charging Control(PCC) rules and Service Data Flow (SDF) filters from the PCRF to thePGW.
 3. The PGW network node of claim 2, where the NAT64-ALGfunctionality module and the PGW are further configured to translatebetween IPv4 and IPv6 SDF filters.
 4. The PGW network node of claim 1,further comprising a NAT64 Network Address and Port Translation (NAPT)table.
 5. The PGW network node of claim 1, further comprising an S2binterface toward an Evolved Packet Data Gateway (ePDG) network node. 6.The PGW network node of claim 1, further comprising an S5/S8 interfacetoward a Serving Gateway (SGW) network node.
 7. The PGW network node ofclaim 1, further comprising an Gn/Gp interface toward a Serving GPRSSupport Node (SGSN) network node.
 8. The PGW network node of claim 1,wherein the application node of the IMS comprises an ApplicationFunction (AF).
 9. A Packet Data Network Gateway (PGW) network node of anEvolved Packet Core (EPC) for connecting a User Equipment (UE) with anIP Multimedia Core Network Subsystem (IMS), comprising: a Gx interfacetoward a Policy Control and Charging Rules Function (PCRF) network nodeconfigured to transmit the UE's IPv4 address to the PCRF; an SGiinterface toward an application node of the IMS configured the UE's IPv4address to the application node, and to transmit and receive IP mediapackets between the IMS and the UE after IPv4 and IPv6 addresstranslation; and a processor including: an IP address assignmentfunction configured to assign both IPv4 and IPv6 addresses to the UErequesting an IPv6 address; and a Network AddressTranslation-Application Layer Gateway (NAT64-ALG) function configured totranslate between IPv4 and IPv6 addresses of the UE.
 10. The PGW networknode of claim 9, wherein the Gx interface is further configured toprovision Policy and Charging Control (PCC) rules and Service Data Flow(SDF) filters from the PCRF to the PGW.
 11. The PGW network node ofclaim 10, where the NAT64-ALG function is further configured totranslate between IPv4 and IPv6 SDF filters.
 12. The PGW network node ofclaim 9, further comprising a NAT64 Network Address and Port Translation(NAPT) table.
 13. The PGW network node of claim 9, further comprising anS2b interface toward an Evolved Packet Data Gateway (ePDG) network node.14. A computer-implemented method in a Packet Data Network Gateway (PGW)of an Evolved Packet Core (EPC) for interfacing with an IP MultimediaCore Network Subsystem (IMS), comprising: assigning both IPv4 and IPv6addresses to a User Equipment (UE) requesting an IPv6 address; providingIPv4 and IPv6 address and Service Data Flow (SDF) filter translation;providing a Gx interface toward a Policy Control and Charging RulesFunction (PCRF) network node configured to transmit the UE's IPv4address to the PCRF; and providing an SGi interface toward anapplication node of the IMS, providing the UE's IPv4 address to theapplication node over the SGi interface, and transmitting and receivingIP media packets between the IMS and the UE after IPv4 and IPv6 addresstranslation.
 15. The computer-implemented method of claim 14, whereinproviding the Gx interface further comprises provisioning Policy andCharging Control (PCC) rules and Service Data Flow (SDF) filters fromthe PCRF.
 16. The computer-implemented method of claim 14, furthercomprising accessing a NAT64 Network Address and Port Translation (NAPT)table for translating the IPv4 and IPv6 addresses.
 17. Thecomputer-implemented method of claim 14, further comprising providing anS2b interface toward an Evolved Packet Data Gateway (ePDG) network node.18. The computer-implemented method of claim 14, further comprisingproviding an S5/S8 interface toward a Serving Gateway (SGW) networknode.
 19. computer-implemented method of claim 14, further comprisingproviding an Gn/Gp interface toward a Serving GPRS Support Node (SGSN)network node.